Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of wind using known airfoil principles. For example, rotor blades typically have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade producing a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is connected to a generator for producing electricity.
The rotor blades are typically constructed of a fiberglass composite material formed using one or more molds. For example, the blade halves of a conventional rotor blade are typically formed in large molds that are custom made for the particular size and shape of the rotor blade being produced. More specifically, various rotor blades may be constructed using Resin Transfer Molding (RTM), such as Vacuum Assisted Resin Transfer Molding (VARTM). With the VARTM process, composite parts are made by placing dry fiber reinforcing fabrics and a core material into an open mold, enclosing the mold into a vacuum bag, and drawing a vacuum in order to ensure a complete preform infiltration with resin. The mold is then heated to allow the part(s) to cure. Blade halves can then be joined together to form the rotor blade.
After the rotor blade is assembled and cured, the completed blade is then typically painted. Painting the rotor blade after it has been removed from the mold allows for an inspection of the finished blade to confirm whether there are surface defects such as dry glass, porosity, or waves. In some instances, painting costs could be reduced if pigmented gel coats were used instead of paint. Such gel coats, however, make inspection of the rotor blade surface impossible.
In view of the aforementioned issues, there is a need for improved methods for manufacturing rotor blades. For example, a method for manufacturing a rotor blade using a gel coat with a changeable pigment would be advantageous.